The present invention is related to an image sensor with a protective package structure for a sensing area, and more particularly to an image sensor with a flip chip package in which a dike is formed around the image-sensing area of the chip for isolating the image-sensing area from contamination and scattering light beam.
It is a trend to use flip chip packaging. In such a manufacturing procedure, bumps are formed on the wafer. Then, after being cut into units, the units are loop soldered with the circuit contact on the substrate. This can achieve a minimum package volume for the size of chip. In addition, the chip can directly radiate heat. Accordingly, the flip chip package meets the requirement of miniaturization for current electronic products.
FIG. 10 shows a conventional flip chip package structure for an image sensor. A conductive interconnection circuit 81 is formed on the lower face of a glass substrate 80. Multiple solder pads are disposed on the chip of a semiconductor image sensor. By means of thermopressing or loop soldering, via tin balls 82 or bumps, the solder pads are electrically connected with the circuit contacts of the conductive interconnection circuit 81. The perimeter of the chip are underfilled with gum material 83 for obtaining an airtight effect. A tin ball is implanted in each circuit contact of the peripheral area of the glass substrate for adhering to the surface of the circuit board. The above arrangement has some shortcomings as follows:                1. The underfilled gum material infiltrates into the gap between the chip and the glass substrate by means of capillary action. In cases where the gum material is not properly controlled, the image sensing area of the chip may be partially or totally covered by the gum material. This will affect the optical path of the image projected to the image sensing area. As a result, the sensed image will be fogged.        2. Light can still pass through the glass substrate outside the perimeter of the image sensing area of the chip as shown in FIG. 11. However, the picked up image light beams T1, T2 are partially reflected by the surface of the chip and fully reflected by the lower surface of the glass substrate and then projected to the image sensing area. This will interfere with the image sensed around the image sensing area.        3. In the case where the image sensing area the chip is associated with the glass substrate by means of tin paste loop soldering or lead/tin bumps, a flux is often painted on the soldered surface. At this time, the gas of the volatile solvent of the flux when exposed to high temperatures will partially escape into the image sensing area. This will contaminate or vaporize the image sensing area. As a result, the quality of the picked up image will be directly affected.        